Voice-operated relay equipment



July 19,1927. 1,636,031"

s'. B. WRIGHT VOICE OPERATED RELAY EQUIPMENT Filed Nov. e, 1925 his INVEN TOR 5.3. W g/w jacent Patented July 19, 1927. v

uurran STATES PATENT OFFICE.

SUMNER B. WRIGHT, OE EAST ORANGE, NEW JERSEY, ASSIGNOR TO AMERICAN TELE- PHONE AND TELEGRAPH COMPANY, A CORPORATION OF NEW YORK.

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Application filed November 6, 1925. Serial 110, 67,400.

This invention relates to voice-operated relay circuits of the typeused in echo suppressing equipment, voice-operated repeater circuits, and the like.

Tests have shown that steady currents, such as those set up in telephone circuits by .induction' from power lines and other adsensitivity at which a voice-operated circuit such as an echo suppressor can be worked. The seriousness of this ditficulty becomes apparent when it is considered that the sensitivity of an echo suppressor, for example, is limited by the noisiest circuit which may be connected to the echo suppressor at any given time, although for a large number of other connections 'a greater sensitivity would be possible.

One of the objects of this invention is to provide a-voice-operated relay circuit which will be substantially non-responsive to steady noise currents, but which will be quite sensitive to voice currents even though the voice currents be of very small magnitude. The invention takes advantage of the fact that the noise currents aresteady and continuous,

whereas the voice currents which are intended to operate the relay are fluctuating currents.

' This and other objects of the invention are attained by means of the arrangements setforth in detail in the following description and illustrated'in the accompanying drawing, the figure of which illustrates the preferred embodiment of the invention.

Referring to the drawing, LE andLW designate transmission paths such as one-way paths of a 22 repeater or the one-waylines of a four-wire circuit. In the operation of such circuits, it is desirable, in order to prevent 'echos when talking over one of the paths, that apparatus shall be operated to disable the path transmitting in the opposite direction. In the drawing, voice-operated apparatusis illustrated associated wlth one of the paths to disable the opposite path. It will he understood, of course, that similar apparatus is associated with the second path to disable the first path when transmission is taking place over the second path.

The voice-operated equipments bridged across the path LE through atransformer' T in series with which is the ca acity' 20 so as to make the apparatus ine cient at frequencies for which the continuous disturbcircuits are a serious limitation on the ing currents are strongest. The current passing through the transformer will, therefore, be principally voice energy as istinguished from the noise energy. On the secondary side of the transformer the circuit divides so that part of the energy. passes over an upper path to a resistancelt, and

thence through a transformer T "to.*the input of a detector D Part or theenergy is also transmitted through a lower pathlwhich includes a delay network N, and after passing through the network to the resistance R the energy is transmitted through the transformer T to the input circuit 'of'the detector D The" delay net'workN. may be of any type well known in the art.

The detectors may have their gridpotentials normally adjusted to such values that when no'alternating current is applied to the detectors, no direct current flows in the output circuits thereof. Consequently, when alternating current is applied tov the detectors, rectified pulses of direct current flow in the output circuits. The output circuits of the two detectors include separate windings of a differential relay 30.

Now, if the actuating currents impressed upon the detectors are continuous, as in the case of noise due to power circuits, equal currents will flow in the two windings of the throughthe delay network to the input of the detector D,. By the time the change in space current of the detector D correspondingv to this pulse occurs, the relay 30 is already operated to release the relay 31 and short-circuit the path LW. Depending on the length of the voice current impulse, the detected pulse in the'output circuit of the detector D may arrive at such time as to producea magnetic flux opposing that due to the detector D to release the armature of the relay 30, or it may arrive after the impulse due to the detector D has ceased, in which case the impulse due to the detector D 'will operate to hold up the armature of the relay 30, or if it is already released, to again pull it up. If the armature is released momentarily, it does not disturb the effectiveness of plied to the two detectors will be to main- This slight lengthenin the short-circuit applied to the path LW, as the relay 31 is made slow to operate. If the delayed impulse arrives at such time as to have the effect of holding the armature of relay 30 up longer, its only result is to slightly lengthen the period required, after an impulse has ceased, to remove the disabling short-circuit from the disabled path. of the restoration period is not objectiona 1e, and may, in gen-- eral. be desirable.

The delay due to the network N will, in general, be but a small fraction of a second, merely long enough to enable the differential relay to'operate before the delayed impulse arrives. The voice current pulses due to different syllables of words will follow each other fairly rapidly with the result that an operating pulse of detected current will be effective upon the differential-relay 30 for each voice current ulse. The effect of steady or continuous a ternating currents aptain the same change in space current in the output circuits of the two tubes continuously, with the result that the two windings of the differential relay will opposeeach other an instant after the continuous currents begin and thereafter will continuously oppose each other. arrangement above described will be unresponsive to continuous voice currents which are steady in amplitude for a period longer than the time required for the operation of relay 31, which is made slow for this reason, but will, be effectively responsive to vocal impulses to substantially the same extent as the ordinary voice-operated relay arrangement;

It will be obvious that the general principles herein disclosed may be embodied in many other organizations widely different from those illustrated without departing from the spirit of the invention as define in the following claims.

What is claimed is: 1. In a voice-operated relay circuit, a

It will therefore be clear that the for transmitting voice currents and a ternatin' currents, branches for said path, each branc including a detector, a relay having windings differentially associated with the output side of said detectors and a delay neti work in one of the branches. I

3. In a voice operated relay circuit, a path over which voice currents and steady alternating currents may be transmitted, branches for said path, means in each branch for translating alternating voice currents into one-way pulsating currents, a relay having windings differentially associated with said translating means, and means to cause one branch to transmlt currents with a higher velocity than the other.

.4. In a voice operated relay circuit, a path over which voice currents and steady alternating currents may be transmitted, a plurality of detectors associated therewith, a relay having windings differentially associated with said detectors, and means to cause one deteetorpircuit to respond before the other.

5. In a voice operated relay circuit, a ath over which voice currents and steady a ternating currents may be transmitted, two detectors associated in parallel therewith, a relay having windings differentially associated with said translating means, and means to delay the transmission of currents to the one detector as compared with the other.

In testimony whereof, I have signed m y name to this specification this 4th day of 00 November, 1925.

' SUMNER B. WRIGHT 

